The average cost of some books is $44.
If 5 of the books are now each $12 more,
the average cost of the books becomes $49.
How many books are there altogether?
|
Case 1 |
Case 2 |
Number |
1 u |
1 u |
Value |
44 |
49 |
Total value |
44 u |
49 u |
Number of books at first = 1 u
Number of books in the end = 1 u
Total cost of the books at first
= 44 x 1 u
= 44 u
Total cost of books in the end
= 49 x 1 u
= 49 u
Increase in the cost when 5 books are now each $12 more
= 5 x 12
= $60
Total cost of books after 5 books are now each $12 more
= 44 u + 60
49 u = 44 u + 60
49 u - 44 u = 60
5 u = 60
1 u = 60 ÷ 5 = 12
Number of books in the end
= 1 u
= 12
Answer(s): 12